Lift gas can be pumped into an annulus between a production tubing and surrounding well casing and subsequently into the production tubing from the annulus via one or more one way gas lift flow control devices in side pockets that are distributed along the length of the production tubing. The lift gas which is injected through the flow control devices into the crude oil (or other fluid) stream in the production conduit reduces the density of the fluid column in the production conduit and enhances the crude oil production rate of the well.
Gas lift flow control devices can use one way check valves which comprise a flapper type valve that presses against a seating. They can also include a ball or hemisphere or cone which is pressed against a valve seating ring by a spring. If the lift gas pressure is higher than the pressure of the crude oil stream in the production conduit then this pressure difference exceeds the forces exerted to the check valve by the spring so that the spring is compressed and the valve is opened and lift gas is permitted to flow from the gas filled injection conduit into the production conduit. If however the pressure of the crude oil stream is higher than the lift gas pressure in the injection conduit, the accumulated forces of the spring and the pressure difference across the gas lift flow control device closes the check valve and prevents crude oil, or other fluid, to flow from the production conduit into the injection conduit.
Issues exist relating to integrity of the sealing function of the one way valve, particularly across a wide range of pressure differentials, e.g., zero to high pressure differential. Also, issues exist with degradation of the seals through exposure to flow of gas and well fluids for various reasons, e.g., debris in the flow.
Accordingly, it is desirable to improve the sealing of the one way valve, and also to protect the integrity of the sealing components during flow of the gas and operation in general.